The present invention relates generally to compositions effective for destroying hazardous compounds and, more particularly, to compositions effective to catalyzing the oxidation of organophosphorus compounds, including chemical warfare agents, pesticides and solvents.
Numerous catalysts have been studied over the years for the decomposition of hazardous compounds. However, one of the difficulties in the practical application of a catalyst is the fact that the catalyst may degrade or become poisoned over time. In several cases, a reaction product causes poisoning of the catalyst due to strong adsorption on the catalyst surface, and further reaction is impeded. Specifically, organophosphonate-type compounds, such as chemical warfare agents and pesticides, are known to cause catalyst poisoning because phosphorus species tend to bind strongly to catalytically active sites.
Various patents disclose methods for the destruction of hazardous wastes, toxic compounds and chemical warfare agents. U.S. Pat. No. 5,451,738 discloses the plasma arc decomposition of hazardous wastes into vitrified solids and non-hazardous gasses. U.S. Pat. No. 5,545,799 describes the chemical destruction of toxic organic compounds by means of an oxidizing reaction between, for example a chlorine-containing or arsenic-containing compound, and an oxidizing agent, for example hydrogen peroxide at a temperature of 50-90xc2x0 C., and at specific pHs. U.S. Pat. No. 5,760,089 discloses a chemical warfare agent decontaminant solution using quaternary ammonium complexes. WO Patent 9718858 describes a method and apparatus for destroying chemical warfare agents based on reaction with a nitrogenous base containing solvated electrons.
U.S. Pat. No. 4,871,526 describes the heterogeneous catalytic oxidation of organophosphonate esters using a molybdenum catalyst. As disclosed therein, the reaction results in the production of carbon monoxide and phosphorus oxide(s) without the undesired accumulation of carbonaceous or phosphorus overlayers on the molybdenum surface. In fact, molybdenum is one of the only species shown to be resistant to poisoning by phosphorus compounds.
European Patent 0501364 discloses a low chromium activated charcoal for destroying chemical warfare agents. As disclosed therein, the amount of active metal, such as chromium VI, in the activated charcoal or ASC whetlerite charcoal catalyst is reduced by as much as 50% via a freeze-drying technique without reducing the activity of the charcoal. These materials are used in providing protection against chemical warfare agents but because chromium VI is a known carcinogen, disposal of the spent charcoal is a problem.
Several studies have been reported on the catalytic decomposition of DMMP on various catalysts, including Ni (1 1 1), Pd (1 1 1), Rh (1 0 0), Al2O3, Mo (1 0 0), Fe2O3, SiO2 and Pt. In most of the studies, with the exception of Mo (1 0 0), the catalytic reaction was not sustained due to accumulation of products on the catalyst surface. In the case of Mo (1 0 0) in the presence of O2, phosphorous oxide and carbon monoxide were observed as products at high temperatures (roughly 520xc2x0 C.). Rather than phosphorus-containing compounds on the surface, only O2 was measured on the catalyst surface. However, if O2 was not used in the reaction, phosphorus-containing species were found to accumulate on the surface. The proposed catalyst may be doped with Mo in order to enhance sustained catalytic activity and to reduce degradation. In addition, the use of an oxygen or air purge may be employed.
Others have studied various supports for AMO such as zeolites, clays, Al2O3, SiO2, V2O5, CaO, TiO2, with C and MgO showing significantly greater activity than the others Manganese oxides are unique compared to most other oxides such as SiO2 and Al2O3. For example, in the reaction of DMMP on silica, others have found that DMMP desorbs molecularly at high temperatures rather than decomposing. Alumina, as well, was found to be only marginally effective in the decomposition of DMMP. The use of iron oxide, however, proved to be more effective because the iron may be reduced.
It is an object of the present invention to provide compositions effective for catalyzing the destruction of organophosphorus compounds including chemical warfare agents, pesticides, and solvents. As used herein, destruction means the chemical decomposition or conversion to relatively non-toxic products.
In accordance with the present invention, there is provided a composition comprising a catalyst material selected from the group consisting of vanadium oxide or manganese oxide deposited upon a catalyst support selected from the group consisting of alumina or silica.